Rear axle was upgraded from the stock unit to a Ford 9 inch from a 1960 Ford F100 truck. The original axle had gears of 3.92 which are good for flatheads but not good if you want to go over 45 miles an hour and different gearsets are not available for these early axles. The replacement axle bolted in with no changes to the spring pads but I did have to shim the pinion to get the 5 degrees I wanted to match the engine setup. These axles are the same width and all the emergency brake parts match up.